1. Field of the invention
The present invention relates, in general, to a method for producing different hydrofluorocarbons, simultaneously and, more particularly, to the use of a series of different reactors, each suitable for operating its own characteristic reaction process for the production of the individual hydrofluorocarbon.
2. Description of the Prior Art
Chlorofluorocarbon (hereinafter referred to as "CFC") compounds, extensively used for many purposes such as foaming agents, detergents, aerosol spraying agents and refrigerants, are destined to be prohibited from production and use in a few years in accordance with the internationally agreed protocol as they were proven to be a main factor destroying the ozone layer of the stratosphere. Accordingly, intensive research and study have been directed to the development of the substitutes that are not harmful to the ozone layer and functionally equal to CFC. As a result of extensive test for toxicity, stability and physicochemical performance, hydrofluorocarbon(HFC) compounds such as diflouromethane (HFC-32), trifluoromethane (HFC-23), 1,1-difluoroethane (HFC-152a), 1,1,1-trifluoroethane (HFC-143a), 1,1, 1,2-tetrafluoroethane (HFC-134a) and pentafluoroethane (HFC-125) were revealed to be potent substitutes for CFC. Of them, HFC-134a turned out to be able to replace dichlorodifluoromethane (CFC-12) and thus, it is already in commercial production. Yet the use of other compounds have not been sufficiently developed. At most there have been attempts to use a mixture of them as special refrigerants, for example, a mixture of HFC-134a, HFC-32 and HFC-143a, or of HFC-134a, HFC-32 and HFC-125 as a cooling agent.
Various methods were suggested to produce HFC compounds. For example, the methods disclosed in European Patent Nos. 0 449 614 A2 and 0 449 617 A2 and Korean Laid-Open Patent Publication No. 91-16657 are useful for the production of HFC compound, but only for one particular compound. The cited European patents record that HFC-134a can be produced from trichloroethylene (TCE) and hydrogenfluoride through a two-step reaction. It is written in the cited Korean patent that, when HFC-134a is produced from TCE and hydrogenfluoride through a two-step reaction, an addition of an inert gas to the reaction allows the reaction temperature to be controlled easily in addition to lowering the production of 1,1-difluoroethylene, a by-product.
Canadian Patent No. 1 196 345 discloses a method for the production of fluorinated carbons by which different products, such as HFC-134a, HFC-143a, HFC-125 and HCFC-133a, are produced from different reactants at different reaction temperatures in the presence of the same catalyst, composed of chromium fluoroxide. Likewise, U.S. Pat. No. 1,000,485 discloses that various kinds of hydrochlorofluoro carbons are produced from various reactants at appropriate reaction temperatures in the presence of aluminium fluoride catalyst.
Those methods disclosed in the above-cited patents, which produces one particular product from a particular reactant material, are quite different from the present invention in which at least two kinds of hydrofluoro carbons can be obtained, simultaneously.
Meanwhile, since an enormous capital investment is required for building a plant for the substitutes for CFC, it is not economical unless the production scale is significantly large. However, it seems likely that the construction of such a large plant is accompanied by great risk, when the large demand for the CFC substitutes is hard to be expected in the near future.